cleanup.

mainly to avoid the pattern of
* get username/hostname/rolename
* optionally find the corresponding ACL_USER and ACL_ROLE
* allocate memory, concatenate username/hostname/rolename
* call a function passing only this memory as an argument
** use concatenated username/etc to find ACL_USER and ACL_ROLE again
** do something
* free the object

Also to undo push_dynamic we use pop_dynamic now,
not a linear search/scan through the dynamic array.

as a bonus, role@ is now an invalid way to refer to a role.

mysql-test/r/acl_roles_set_role-recursive.result

@@ -2,7 +2,7 @@ create user test_user@localhost;
 create role test_role1;
 grant test_role1 to test_user@localhost;
 create role test_role2;
-grant test_role2 to test_role1@;
+grant test_role2 to test_role1;
 select user, host from mysql.user where user not like 'root';
 user	host
 test_role1	

mysql-test/r/acl_roles_set_role-table-column-priv.result

@@ -2,7 +2,7 @@ create user test_user@localhost;
 create role test_role1;
 create role test_role2;
 grant test_role1 to test_user@localhost;
-grant test_role2 to test_role1@;
+grant test_role2 to test_role1;
 select user, host from mysql.user where user not like 'root';
 user	host
 test_role1	

mysql-test/r/acl_roles_set_role-table-simple.result

@@ -2,7 +2,7 @@ create user test_user@localhost;
 create role test_role1;
 create role test_role2;
 grant test_role1 to test_user@localhost;
-grant test_role2 to test_role1@;
+grant test_role2 to test_role1;
 select user, host from mysql.user where user not like 'root';
 user	host
 test_role1	

mysql-test/r/acl_roles_show_grants.result

@@ -3,7 +3,7 @@ create role test_role1;
 create role test_role2;
 grant test_role1 to test_user@localhost;
 grant test_role2 to test_user@localhost;
-grant test_role2 to test_role1@;
+grant test_role2 to test_role1;
 select user, host from mysql.user where user not like 'root';
 user	host
 test_role1	

mysql-test/t/acl_roles_set_role-recursive.test

@@ -4,7 +4,7 @@ create user test_user@localhost;
 create role test_role1;
 grant test_role1 to test_user@localhost;
 create role test_role2;
-grant test_role2 to test_role1@;
+grant test_role2 to test_role1;
 
 --sorted_result
 select user, host from mysql.user where user not like 'root';

mysql-test/t/acl_roles_set_role-table-column-priv.test

@@ -3,7 +3,7 @@ create role test_role1;
 create role test_role2;
 
 grant test_role1 to test_user@localhost;
-grant test_role2 to test_role1@;
+grant test_role2 to test_role1;
 --sorted_result
 select user, host from mysql.user where user not like 'root';
 --sorted_result

mysql-test/t/acl_roles_set_role-table-simple.test

@@ -3,7 +3,7 @@ create role test_role1;
 create role test_role2;
 
 grant test_role1 to test_user@localhost;
-grant test_role2 to test_role1@;
+grant test_role2 to test_role1;
 --sorted_result
 select user, host from mysql.user where user not like 'root';
 --sorted_result

mysql-test/t/acl_roles_show_grants.test

@@ -5,7 +5,7 @@ create role test_role2;
 
 grant test_role1 to test_user@localhost;
 grant test_role2 to test_user@localhost;
-grant test_role2 to test_role1@;
+grant test_role2 to test_role1;
 --sorted_result
 select user, host from mysql.user where user not like 'root';
 --sorted_result